Thank you for being so patient with me. The problem is solved now. If I believed in gods, I would call you a retropie god. I guess Global Moderator will have to do.
"that's why I asked for a complete log (including ES exiting)." I was giving you what ES was producing.
I launched ES from terminal with the command emulationstation --debug
I went and scraped the snes ROMS - data and images were retrieved.
Exited ES and restarted it with just the emulationstation command
copied the es_log.txt file to a rom folder - so I could transfer it to my PC
How I fixed the problem:
Moved the SNES ROM's to a folder called SNESBAK
There was no /snes/gamelist.xml file
I found a bucket load of image files in /home/pi/.emulationstation/downloaded_images/snes/ I deleted them all
I rebooted retropie
Copied the snes ROMs from the SNESBAK folder to the snes folder
restarted ES
Tried scraping 10 of the snes ROMS and was succesful
Restarted ES and the 10 ROM's data and images were saved.
Deleted SNESBAK and ROMS